Ubc9-mediated sumoylation leads to transcriptional repression of IRF-1.
To characterize the regulatory mechanism of the interferon regulatory factor (IRF) family, we performed yeast two-hybrid screening with IRF-2 and isolated the small ubiquitin-related modifier (SUMO)-conjugating enzyme Ubc9, which also interacts with other IRF family members IRF-1 and ICSBP. Subsequent assays indicated that among the IRF family members, only IRF-1 interacts with SUMO-1 through its transcriptional activation domain. The interaction between IRF-1 and SUMO-1 was confirmed in vitro by GST pull-down assays and in vivo by co-localization assays. Furthermore, this interaction led to the Ubc9-mediated sumoylation of IRF-1 in vitro and in vivo. Transient transfection assays revealed that Ubc9 or SUMO inhibits the transcriptional activity of IRF-1 in a dose-dependent manner. Finally, Ubc9 and SUMO cooperate in the transcriptional repression of IRF-1. Taken together, these observations suggest that Ubc9 functions as a transcriptional repressor of IRF-1 by inducing sumoylation, and that this effect may be required for the physiological activity of IRF-1.
Kim
Eun-Joo
EJ
Department of Molecular Biology, Dankook University, Gyeonggi-do 448-701, Republic of Korea.
Park
Jong-Sup
JS
Um
Soo-Jong
SJ
D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000235:genetics*; D050836:Interferon Regulatory Factor-2 / Q000235:genetics; D051379:Mice; D041681:NIH 3T3 Cells; D012097:Repressor Proteins / Q000378:metabolism*; D025842:SUMO-1 Protein / Q000378:metabolism*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D000098843:Ubiquitin-Conjugating Enzyme UBC9
D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; C494258:Irf1 protein, mouse; D012097:Repressor Proteins; D025842:SUMO-1 Protein; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9